1. Field of the Invention
The invention relates to rectal balloons that are used for immobilizing the region surrounding the prostate.
2. Description of the Related Art
Treatment of prostate cancer using radiation therapy is difficult due to the prostate's position near radiation-sensitive tissues, and is further complicated by prostate motion. Adenocarcinoma of the prostate commonly occurs in the posterior portion of the prostate gland which is in very close proximity to the rectal wall. To plan external beam radiation treatment, urethrograms, CT scans and magnetic resonance imaging (MRI) have all been used to visually localize the prostate, as well as the normal critical structures in the surrounding area.
U.S. Pat. No. 5,476,095, issued on Dec. 19, 1995 to Schnall et al., describes an insertable pickup probe for use in providing diagnostic MRI images. The pickup probe in its preferred embodiment is for use in imaging the male prostate and comprises an elongated shaft supporting an inflatable patient interface balloon at its distal end. The interface balloon comprises an inner balloon and an outer balloon, between which a receiving coil is positioned. A lumen for air supply is provided in the shaft for expanding the inner balloon against the outer balloon to place the receiving coil in close proximity to the area of interest in order to provide MRI images.
Typically, the planning of radiation therapy for the treatment of prostate cancer involves the patient undergoing a CT-based simulation scan of the pelvis to determine the location of the prostate gland. In the simulation phase, the patient is placed on CT equipment that is preferably similar to the radiation treatment equipment (except that it does not generate the high energy radiation beam). The simulation equipment is positioned to simulate the delivery of the sequence of treatment beams prescribed by the treating oncologist. Normally, during the simulation procedure, CT images are acquired. These CT images allow the oncologist to locate the position of the tumor and help to facilitate the composition of a radiation treatment plan. This treatment plan delineates the positions of the radiation equipment components for delivery of the treatment beams.
During the actual treatment phase, the patient is placed in the same position on the treatment equipment as in the simulation scans. Radiation-emitting devices are generally known and used for radiation therapy in the treatment of patients. Typically, a radiation therapy device includes a gantry, which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high-energy radiation beam for therapy. During treatment, the radiation beam is provided by this equipment and is delivered to the patient at the precise location as delineated by the physician during simulation. A further feature of radiation therapy involves portal images, which are commonly used in radiation therapy to verify and record the patient tumor location. Portal images include manual (film) and electronic images (EPI) taken before and/or after the treatment.
During external beam radiation therapy, radiation is directed to the target prostate which is near the rectal wall. A misdirected radiation beam may perforate the rectal wall causing radiation proctitus (rectal bleeding). This toxicity is related to the total radiation dose prescribed and the volume of the anterior rectal wall receiving a high radiation dose. A major factor limiting radiation oncologists' attempts to reduce the volume of the anterior rectal wall receiving a high radiation dose is the position of the prostate gland as well as the intrinsic motion up to 5 mm in the anterior to posterior direction caused by rectal peristalsis. Accordingly, oncologists generally will add a margin to the radiation field in order to ensure that the entire prostate gland receives the prescription dose. This margin is typically on the order of 5 to 15 mm. As a consequence, lower doses of radiation may need to be used so as not to overexpose radiation sensitive structures. However, this may lead to inadequate radiation treatment and a higher probability of local cancer recurrence.
U.S. Patent Publication No. 2003/0028097, published on Feb. 6, 2003 to D'Amico et al., describes an immobilizer probe system and method. This system has an insertable probe for immobilizing a region of interest during staging and radiation therapy thereof. In particular, this device uses a balloon having a rectangular cross section connected to a shaft. The shaft extends to an end of the balloon so as to allow fluid flow through an interior of the shaft and into the balloon so as to selectively inflate the balloon once the balloon is installed into the rectal cavity. The balloon, shaft and handle are bonded together so that they move radially as a single unit when torque is applied. A syringe is provided which connects the shaft and serves as an air pump to deliver a volume-limited amount of air to the air lumen of the shaft to the balloon. A stop cock is provided to maintain the air within the balloon.
One of the problems with the subject of U.S. Patent Publication No. 2003/0028097 is the discomfort associated installing the rectal balloon within the rectal cavity. In particular, a relatively sturdy and wide diameter shaft is connected to a relatively large thick-walled balloon. Because the balloon is not supported by anything other than by the shaft, the balloon is formed of a relatively rugged and thick material. Because of the relatively large size of the shaft and the thick material of the rectangular-cross section balloon, the installation of the rectal balloon creates a large amount of discomfort for a patient. It is often difficult for the medical personnel to know exactly how far within the rectum the balloon has been installed. It is difficult to achieve a standardized and fixed position of the balloon during each and every use. The medical personnel must generally approximate the desired position of the balloon within the rectal cavity. As such, a need has developed whereby the rectal balloon can be formed of a minimal diameter shaft and of a balloon of relatively thin material.
When the rectal balloon of U.S. Patent Publication No. 2003/0028097 is in an inflated condition, the outer surface is generally round. As such, the prostate will tend to balance on the curved surface rather than properly seating thereon. Since seating is important for proper use, this device requires that the physician approximate a seated position rather than providing any feedback of the seated position. When the balloon is in a curved inflated condition, the prostate will have a tendency to slide to one side of the balloon. As such, a need developed to provide a rectal balloon that retains the prostate in a proper seated position when the balloon is in a fully inflated condition.
It is an object of the invention to provide a rectal balloon apparatus which is easy to use and easy to install.
It is another object of the invention to provide a rectal balloon apparatus whereby the position of the balloon can be easily ascertained by medical personnel.
It is a further object of the invention to provide a rectal balloon apparatus which maximizes the comfort to the patient.
It is a further object of the invention to provide a rectal balloon apparatus which has better holding stability when inflated.
It is a further object of the invention to provide a rectal balloon apparatus which has a flexible shaft.
It is another object of the invention to provide a rectal balloon apparatus which can be inflated to several configurations for different medical purposes.
It is another object of the invention to provide a rectal balloon apparatus which enhances the ability to properly seat the prostate on a flat surface of the rectal balloon.
It is a further object of the invention to provide a rectal balloon apparatus which avoids potential allergic reactions.
It is still a further object of the invention to provide a rectal balloon apparatus which is easy to manufacture and relatively inexpensive.
These and other objects and advantages of the invention will become apparent from a reading of the attached specification and appended claims.